phosphor

Examples of phosphor in the following topics:

• The Phosphorus Cycle

  • Plants assimilate phosphorous from the environment and then convert it from inorganic phosphorous to organic phosphorous.
  • The organic phosphorous is released and converted back into inorganic phosphorous through decomposition.
  • Much of the phosphorous is then converted to organic phosphorous, and primary productivity then declines.
  • The phosphorous cycle is affected by human activities.
  • Although phosphorous is normally a limiting nutrient, most agricultural fertilizers contain phosphorous.

• Cathode Ray Tube, TV and Computer Monitors, and the Oscilloscope

  • The images are generated when electrons strike fluorescent phosphors on the screen, which then emit light (the color varies depending on the phosphor used, ).
  • By varying the type of phosphor used, one may vary the wavelength of light emitted by the phosphor when excited.
  • Early computer terminal monitors used only green phosphors.
  • For visual observation of brief transient events, a long persistence phosphor may be desirable.
  • Monochrome monitor - this CRT uses only one type of phosphor.

• Phosphorus Compounds

  • For this purpose, phosphate-containing minerals are converted to phosphoric acid.
  • Although many oxoacids of phosphorus are formed, only nine are important, and three are crucial: hypophosphorous acid, phosphorous acid, and phosphoric acid.
  • Phosphorous acid, H3PO3, contains two acidic OH bonds and one PH bond.
  • Since it is triprotic, phosphoric acid converts stepwise to three conjugate bases:
  • Phosphoric acid contains one P=O double bond and three P-O single bonds terminating in acidic OH groups.

• Sources and Sinks of Essential Elements

  • The nitrogen cycle, the phosphorous cycle, the sulfur cycle, and the carbon cycle all involve assimilation of these nutrients into living things.
  • Likewise, phosphorous and nitrogen are extracted from geological reservoirs and used in phosphorous, and excesses of these elements have caused the overgrowth of plant matter and the disruption of many ecosystems.

• Calculating Equilibrium Concentrations of Polyprotic Acids

  • Common polyprotic acids include sulfuric acid (H2SO4), and phosphoric acid (H3PO4).
  • Thus, in an aqueous solution of phosphoric acid, there will theoretically be seven ionic and molecular species present: H3PO4, H2PO4-, HPO42-, PO43-, H2O, H+, and OH-.
  • Take for instance the second dissociation step of phosphoric acid, which has a pKa2 of 7.21:
  • The chemical structure of phosphoric acid indicates it has three acidic protons.

• Alloys

  • Examples of alloys include materials such as brass, pewter, phosphor bronze, amalgam, and steel.
  • Examples of alloys include materials such as brass, pewter, phosphor bronze, amalgam, and steel.

• Nucleophilicity of Phosphorus Compounds

  • Phosphorous analogs of amines are called phosphines.

• Diprotic and Polyprotic Acids

  • Two common examples are carbonic acid (H2CO3, which has two acidic protons and is therefore a diprotic acid) and phosphoric acid (H3PO4, which has three acidic protons and is therefore a triprotic acid).
  • Take, for example the three dissociation steps of the common triprotic acid phosphoric acid:

• Mercury

  • It is also used in lighting—electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light, causing the phosphor to fluoresce and produce visible light.

• Elimination Reactions of Alcohols

  • The conjugate bases of sulfuric and phosphoric acids are not good nucleophiles and do not give substitution under the usual conditions of their use.
  • The E2 elimination of 3º-alcohols under relatively non-acidic conditions may be accomplished by treatment with phosphorous oxychloride (POCl3) in pyridine.